rpcclient: add Internal client for direct RPC server calls

It has a special `requestF` and a special initialization function, but other
than that it's an absolutely regular WSClient. Can be used to call, can be
used to subscribe. Fixes #2909.

pkg/rpcclient/local.go

@@ -0,0 +1,82 @@
+package rpcclient
+
+import (
+	"context"
+
+	"github.com/nspcc-dev/neo-go/pkg/neorpc"
+	"go.uber.org/atomic"
+)
+
+// InternalHook is a function signature that is required to create a local client
+// (see NewInternal). It performs registration of local client's event channel
+// and returns a request handler function.
+type InternalHook func(context.Context, chan<- neorpc.Notification) func(*neorpc.Request) (*neorpc.Response, error)
+
+// Internal is an experimental "local" client that does not connect to RPC via
+// network. It's made for deeply integrated applications like NeoFS that have
+// blockchain running in the same process, so use it only if you know what you're
+// doing. It provides the same interface WSClient does.
+type Internal struct {
+	WSClient
+
+	events chan neorpc.Notification
+}
+
+// NewInternal creates an instance of internal client. It accepts a method
+// provided by RPC server.
+func NewInternal(ctx context.Context, register InternalHook) (*Internal, error) {
+	c := &Internal{
+		WSClient: WSClient{
+			Client:        Client{},
+			Notifications: make(chan Notification),
+
+			shutdown:      make(chan struct{}),
+			done:          make(chan struct{}),
+			closeCalled:   *atomic.NewBool(false),
+			subscriptions: make(map[string]notificationReceiver),
+			receivers:     make(map[interface{}][]string),
+		},
+		events: make(chan neorpc.Notification),
+	}
+
+	err := initClient(ctx, &c.WSClient.Client, "localhost:0", Options{})
+	if err != nil {
+		return nil, err // Can't really happen for internal client.
+	}
+	c.cli = nil
+	go c.eventLoop()
+	// c.ctx is inherited from ctx in fact (see initClient).
+	c.requestF = register(c.ctx, c.events) //nolint:contextcheck // Non-inherited new context, use function like `context.WithXXX` instead
+	return c, nil
+}
+
+func (c *Internal) eventLoop() {
+eventloop:
+	for {
+		select {
+		case <-c.ctx.Done():
+			break eventloop
+		case <-c.shutdown:
+			break eventloop
+		case ev := <-c.events:
+			ntf := Notification{Type: ev.Event}
+			if len(ev.Payload) > 0 {
+				ntf.Value = ev.Payload[0]
+			}
+			c.notifySubscribers(ntf)
+		}
+	}
+	close(c.done)
+	close(c.Notifications)
+	c.ctxCancel()
+	// ctx is cancelled, server is notified and will finish soon.
+drainloop:
+	for {
+		select {
+		case <-c.events:
+		default:
+			break drainloop
+		}
+	}
+	close(c.events)
+}

pkg/rpcclient/local_test.go

@@ -0,0 +1,18 @@
+package rpcclient
+
+import (
+	"context"
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/pkg/neorpc"
+	"github.com/stretchr/testify/require"
+)
+
+func TestInternalClientClose(t *testing.T) {
+	icl, err := NewInternal(context.TODO(), func(ctx context.Context, ch chan<- neorpc.Notification) func(*neorpc.Request) (*neorpc.Response, error) {
+		return nil
+	})
+	require.NoError(t, err)
+	icl.Close()
+	require.NoError(t, icl.GetError())
+}

pkg/rpcclient/wsclient.go

@@ -456,7 +456,7 @@ readloop:
 				connCloseErr = fmt.Errorf("bad event received: %s / %d", event, len(rr.RawParams))
 				break readloop
 			}
-			var val interface{}
+			ntf := Notification{Type: event}
 			switch event {
 			case neorpc.BlockEventID:
 				sr, err := c.StateRootInHeader()
@@ -465,15 +465,15 @@ readloop:
 					connCloseErr = fmt.Errorf("failed to fetch StateRootInHeader: %w", err)
 					break readloop
 				}
-				val = block.New(sr)
+				ntf.Value = block.New(sr)
 			case neorpc.TransactionEventID:
-				val = &transaction.Transaction{}
+				ntf.Value = &transaction.Transaction{}
 			case neorpc.NotificationEventID:
-				val = new(state.ContainedNotificationEvent)
+				ntf.Value = new(state.ContainedNotificationEvent)
 			case neorpc.ExecutionEventID:
-				val = new(state.AppExecResult)
+				ntf.Value = new(state.AppExecResult)
 			case neorpc.NotaryRequestEventID:
-				val = new(result.NotaryRequestEvent)
+				ntf.Value = new(result.NotaryRequestEvent)
 			case neorpc.MissedEventID:
 				// No value.
 			default:
@@ -482,32 +482,14 @@ readloop:
 				break readloop
 			}
 			if event != neorpc.MissedEventID {
-				err = json.Unmarshal(rr.RawParams[0], val)
+				err = json.Unmarshal(rr.RawParams[0], ntf.Value)
 				if err != nil {
 					// Bad event received.
 					connCloseErr = fmt.Errorf("failed to unmarshal event of type %s from JSON: %w", event, err)
 					break readloop
 				}
 			}
-			if event == neorpc.MissedEventID {
-				c.subscriptionsLock.Lock()
-				for rcvr, ids := range c.receivers {
-					c.subscriptions[ids[0]].Close()
-					delete(c.receivers, rcvr)
-				}
-				c.subscriptionsLock.Unlock()
-				continue readloop
-			}
-			c.subscriptionsLock.RLock()
-			ntf := Notification{Type: event, Value: val}
-			for _, ids := range c.receivers {
-				for _, id := range ids {
-					if c.subscriptions[id].TrySend(ntf) {
-						break // strictly one notification per channel
-					}
-				}
-			}
-			c.subscriptionsLock.RUnlock()
+			c.notifySubscribers(ntf)
 		} else if rr.ID != nil && (rr.Error != nil || rr.Result != nil) {
 			id, err := strconv.ParseUint(string(rr.ID), 10, 64)
 			if err != nil {
@@ -580,6 +562,27 @@ writeloop:
 	}
 }
 
+func (c *WSClient) notifySubscribers(ntf Notification) {
+	if ntf.Type == neorpc.MissedEventID {
+		c.subscriptionsLock.Lock()
+		for rcvr, ids := range c.receivers {
+			c.subscriptions[ids[0]].Close()
+			delete(c.receivers, rcvr)
+		}
+		c.subscriptionsLock.Unlock()
+		return
+	}
+	c.subscriptionsLock.RLock()
+	for _, ids := range c.receivers {
+		for _, id := range ids {
+			if c.subscriptions[id].TrySend(ntf) {
+				break // strictly one notification per channel
+			}
+		}
+	}
+	c.subscriptionsLock.RUnlock()
+}
+
 func (c *WSClient) unregisterRespChannel(id uint64) {
 	c.respLock.Lock()
 	defer c.respLock.Unlock()

pkg/services/rpcsrv/client_test.go

@@ -2033,15 +2033,45 @@ func TestClient_Wait(t *testing.T) {
 	check(t, util.Uint256{1, 2, 3}, chain.BlockHeight()-1, true)
 }
 
-func TestWSClient_Wait(t *testing.T) {
+func mkSubsClient(t *testing.T, rpcSrv *Server, httpSrv *httptest.Server, local bool) *rpcclient.WSClient {
+	var (
+		c   *rpcclient.WSClient
+		err error
+		icl *rpcclient.Internal
+	)
+	if local {
+		icl, err = rpcclient.NewInternal(context.Background(), rpcSrv.RegisterLocal)
+	} else {
+		url := "ws" + strings.TrimPrefix(httpSrv.URL, "http") + "/ws"
+		c, err = rpcclient.NewWS(context.Background(), url, rpcclient.Options{})
+	}
+	require.NoError(t, err)
+	if local {
+		c = &icl.WSClient
+	}
+	require.NoError(t, c.Init())
+	return c
+}
+
+func runWSAndLocal(t *testing.T, test func(*testing.T, bool)) {
+	t.Run("ws", func(t *testing.T) {
+		test(t, false)
+	})
+	t.Run("local", func(t *testing.T) {
+		test(t, true)
+	})
+}
+
+func TestSubClientWait(t *testing.T) {
+	runWSAndLocal(t, testSubClientWait)
+}
+
+func testSubClientWait(t *testing.T, local bool) {
 	chain, rpcSrv, httpSrv := initClearServerWithServices(t, false, false, true)
 	defer chain.Close()
 	defer rpcSrv.Shutdown()
 
-	url := "ws" + strings.TrimPrefix(httpSrv.URL, "http") + "/ws"
-	c, err := rpcclient.NewWS(context.Background(), url, rpcclient.Options{})
-	require.NoError(t, err)
-	require.NoError(t, c.Init())
+	c := mkSubsClient(t, rpcSrv, httpSrv, local)
 	acc, err := wallet.NewAccount()
 	require.NoError(t, err)
 	act, err := actor.New(c, []actor.SignerAccount{
@@ -2135,15 +2165,16 @@ func TestWSClient_Wait(t *testing.T) {
 	require.True(t, faultedChecked, "FAULTed transaction wasn't checked")
 }
 
-func TestWSClient_WaitWithLateSubscription(t *testing.T) {
+func TestSubClientWaitWithLateSubscription(t *testing.T) {
+	runWSAndLocal(t, testSubClientWaitWithLateSubscription)
+}
+
+func testSubClientWaitWithLateSubscription(t *testing.T, local bool) {
 	chain, rpcSrv, httpSrv := initClearServerWithServices(t, false, false, true)
 	defer chain.Close()
 	defer rpcSrv.Shutdown()
 
-	url := "ws" + strings.TrimPrefix(httpSrv.URL, "http") + "/ws"
-	c, err := rpcclient.NewWS(context.Background(), url, rpcclient.Options{})
-	require.NoError(t, err)
-	require.NoError(t, c.Init())
+	c := mkSubsClient(t, rpcSrv, httpSrv, local)
 	acc, err := wallet.NewAccount()
 	require.NoError(t, err)
 	act, err := actor.New(c, []actor.SignerAccount{
@@ -2182,15 +2213,16 @@ func TestWSClientHandshakeError(t *testing.T) {
 	require.ErrorContains(t, err, "websocket users limit reached")
 }
 
-func TestWSClient_WaitWithMissedEvent(t *testing.T) {
+func TestSubClientWaitWithMissedEvent(t *testing.T) {
+	runWSAndLocal(t, testSubClientWaitWithMissedEvent)
+}
+
+func testSubClientWaitWithMissedEvent(t *testing.T, local bool) {
 	chain, rpcSrv, httpSrv := initClearServerWithServices(t, false, false, true)
 	defer chain.Close()
 	defer rpcSrv.Shutdown()
 
-	url := "ws" + strings.TrimPrefix(httpSrv.URL, "http") + "/ws"
-	c, err := rpcclient.NewWS(context.Background(), url, rpcclient.Options{})
-	require.NoError(t, err)
-	require.NoError(t, c.Init())
+	c := mkSubsClient(t, rpcSrv, httpSrv, local)
 	acc, err := wallet.NewAccount()
 	require.NoError(t, err)
 	act, err := actor.New(c, []actor.SignerAccount{
@@ -2272,10 +2304,7 @@ func TestWSClient_SubscriptionsCompat(t *testing.T) {
 	defer chain.Close()
 	defer rpcSrv.Shutdown()
 
-	url := "ws" + strings.TrimPrefix(httpSrv.URL, "http") + "/ws"
-	c, err := rpcclient.NewWS(context.Background(), url, rpcclient.Options{})
-	require.NoError(t, err)
-	require.NoError(t, c.Init())
+	c := mkSubsClient(t, rpcSrv, httpSrv, false)
 	blocks := getTestBlocks(t)
 	bCount := uint32(0)
 
@@ -2290,8 +2319,11 @@ func TestWSClient_SubscriptionsCompat(t *testing.T) {
 		return b1, primary, sender, ntfName, st
 	}
 	checkDeprecated := func(t *testing.T, filtered bool) {
+		var (
+			bID, txID, ntfID, aerID string
+			err                     error
+		)
 		b, primary, sender, ntfName, st := getData(t)
-		var bID, txID, ntfID, aerID string
 		if filtered {
 			bID, err = c.SubscribeForNewBlocks(&primary) //nolint:staticcheck // SA1019: c.SubscribeForNewBlocks is deprecated
 			require.NoError(t, err)
@@ -2382,6 +2414,7 @@ func TestWSClient_SubscriptionsCompat(t *testing.T) {
 			txFlt                   *neorpc.TxFilter
 			ntfFlt                  *neorpc.NotificationFilter
 			aerFlt                  *neorpc.ExecutionFilter
+			err                     error
 		)
 		if filtered {
 			bFlt = &neorpc.BlockFilter{Primary: &primary}

pkg/services/rpcsrv/local_test.go

@@ -0,0 +1,57 @@
+package rpcsrv
+
+import (
+	"context"
+	"math/big"
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/internal/testchain"
+	"github.com/nspcc-dev/neo-go/pkg/config"
+	"github.com/nspcc-dev/neo-go/pkg/rpcclient"
+	"github.com/nspcc-dev/neo-go/pkg/rpcclient/actor"
+	"github.com/nspcc-dev/neo-go/pkg/rpcclient/gas"
+	"github.com/nspcc-dev/neo-go/pkg/rpcclient/invoker"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/wallet"
+	"github.com/stretchr/testify/require"
+)
+
+func TestLocalClient(t *testing.T) {
+	_, rpcSrv, _ := initClearServerWithCustomConfig(t, func(cfg *config.Config) {
+		// No addresses configured -> RPC server listens nothing (but it
+		// has MaxGasInvoke, sessions and other stuff).
+		cfg.ApplicationConfiguration.RPC.BasicService.Enabled = true
+		cfg.ApplicationConfiguration.RPC.BasicService.Address = nil //nolint:staticcheck // SA1019: cfg.ApplicationConfiguration.RPC.BasicService.Address is deprecated
+		cfg.ApplicationConfiguration.RPC.BasicService.Port = nil    //nolint:staticcheck // SA1019: cfg.ApplicationConfiguration.RPC.BasicService.Port is deprecated
+		cfg.ApplicationConfiguration.RPC.BasicService.Addresses = nil
+		cfg.ApplicationConfiguration.RPC.TLSConfig.Address = nil //nolint:staticcheck // SA1019: cfg.ApplicationConfiguration.RPC.TLSConfig.Address is deprecated
+		cfg.ApplicationConfiguration.RPC.TLSConfig.Port = nil    //nolint:staticcheck // SA1019: cfg.ApplicationConfiguration.RPC.TLSConfig.Port is deprecated
+		cfg.ApplicationConfiguration.RPC.TLSConfig.Addresses = nil
+	})
+	// RPC server listens nothing (not exposed in any way), but it works for internal clients.
+	c, err := rpcclient.NewInternal(context.TODO(), rpcSrv.RegisterLocal)
+	require.NoError(t, err)
+	require.NoError(t, c.Init())
+
+	// Invokers can use this client.
+	gasReader := gas.NewReader(invoker.New(c, nil))
+	d, err := gasReader.Decimals()
+	require.NoError(t, err)
+	require.EqualValues(t, 8, d)
+
+	// Actors can use it as well
+	priv := testchain.PrivateKeyByID(0)
+	acc := wallet.NewAccountFromPrivateKey(priv)
+	addr := priv.PublicKey().GetScriptHash()
+
+	act, err := actor.NewSimple(c, acc)
+	require.NoError(t, err)
+	gasprom := gas.New(act)
+	txHash, _, err := gasprom.Transfer(addr, util.Uint160{}, big.NewInt(1000), nil)
+	require.NoError(t, err)
+	// No new blocks are produced here, but the tx is OK and is in the mempool.
+	txes, err := c.GetRawMemPool()
+	require.NoError(t, err)
+	require.Equal(t, []util.Uint256{txHash}, txes)
+	// Subscriptions are checked by other tests.
+}